Supervisory signal system



QLSLSLifiLI. K

Oct. 25, 1949. 1. N. MCBAIN I 2,436,360

SUPERVISORY SIGNAL SYSTEM I I I Filed' Nov. 8, 1945 4 2.-Sheetssheet lINVENTOR:

ATTORNEY km NH;

Oct. .25, 1949. l. N. MOBAIN 2,486,360

SUPERVISORY SIGNAL SYSTEM Filed Nov. 8, i945 1 Y I YZ-SheetS-Sheet 2 Fgirm; if Z l0 INVENTOR 1m JVJIcBaim F x; 4m-

ATTORNEY Patented Oct. 25, 1949 SUPERVISORY SIGNAL SYSTEM Ian N. McBain,Sydney, New South Wales, Australia, assignor to Amal tralasia)Australia, Australia gamated Wireless (Aus- Limited, Sydney, New SouthWales, a corporation of New South Wales,

Application November 8, 1945, Serial No. 627,495 In Australia March 8,1945 4 Claims.

This invention relates to superwsory signal systems and moreparticularly to a service signalling arrangement for use in connectionwith commercial telegraph systems.

Devices for transmitting auxiliary signals independently of trafficsignals are well known in the art. It is conventional to use aperforated tape transmitter for trafiic signals and to use an auxiliarykeying device for actuating a bell or other supervisory signal.

In operating a prior art auxiliary keying arrangement, it was possibleto transmit automatically a succession of signals which comprised caseshift and bell ringing signals for producing any number of bell strokes,say from one to five. In this manner, the different service signalscould be transmitted at any time when it was necessary to interrupt theoperation of the tape or traflic transmitter.-

It has been the usual practice heretofore to transmit the same signalsfor bell ringing as for the letter S or J. In order to differentiatebetween the two functions of the same signals, it was necessary,whenever the bell signal was to be transmitted, to precede the same by afigure shift signal and to follow the bell signal by a letter shiftsignal.

The transmission of a signal for each bell stroke thus requires thetransmission of three code signals which are repeated for each stroke ofthe bell.

One of the difliculties which have been encountered in the past is thatthe use of case shift signals in combination with the bell signalsoccasionally resulted in failure of the receiving printer to properlytranscribe code characters following the transmission of the bellsignal. This diiiiculty was encountered because the auxiliary servicesignalling device might break-in on the tape transmitter in the midst oftransmission of upper case characters. The restoration of the printerunit to lower case characters was automatically performed as the lastfunction in the automatic bell signal transmitting unit: Consequentlywhen the tape transmitter resumed its transmission the receiving printerwould be left in the lower case position and would thereby print,incorrectly, characters which were intended to be in the upper caseuntil the tape transmission called for a letter shift signal.

It has also been suggested that the existing methods of transmission andreception be modifled in a manner that would enable the bell signal tobe transmitted and received without resorting to the use of case shiftsignals.

" cordance with this Such an arrangement would no doubt be quitesatisfactory in the case of new services but, involving as it doesmodification of both the transmitting and receiving equipment, itsadoption in the case of existing services is both inconvenient andexpensive.

The object of the present invention is to provide, by simplemodification of existing transmitting apparatus, an arrangement forovercoming the above mentioned difiiculties, and which does not afiectthe conventional requirement of transmitting case shift signals inassociation with auxiliary or service signals, or necessitate anyalteration to existing receiving equipment.

The above mentioned object is achieved, in acinvention, by providing thetransmission of case shift characters from the tape transmitter, forautomatically ensuring that the transmission of signal characters willcontinue in the same case if interrupted by the transmission of Bellsignals until said means is de-energized by opposite case shiftcharacters from said tape transmitter.

The invention will now be described in more detail, reference being madeto the accompanying drawing which shows principally in a single circuitdiagram and by way of example one practical method of modifying knownapparatus in order to carry out the invention. Figs. 1 and 2 should beplaced side by side for ease in tracing the circuits.

Referring to the drawing, therein is shown an arrangement of signallingelements I to. l inclusive of a code element keyer, which are includedwithin the broken line rectangle 8 representing the keyer, theseelements being arranged as contact tongues which are positionable incontact either with positively or with negatively polarized feedercontacts 9, [0 respectively. The tongues I to 1 are arranged to be setin their alternative contacting positions in response to the operationof a set of seeker pins 8a which are controlled in known manner byperforations in the transmitting tape H. The message to be transmittedis first perforated in 7-unit code signals on a paper tape l I which isfed at a cyclic rate through the transmitter T. Different codecombinations are thus set up on the tape controlled tongues for thetransmission of marking or spacing signalling elements in each of theseven positions of a uniform code signal. The code signals thus formedare normally applied toindividual correspondingly designated segments ona multiplex distributor D.

Such a distributor is indicated as having a means, responsive tocodeelement ring RI and a collector ring R3 the latter being connected tothe outgoing line L. Merely by way of illustration, the transmittingdistributor D, having rings RI and R3, is shown in the drawing asarranged for a two channel multiplex system. If the system were intendedfor three or more channels, then the number of segments in thedistributor ring RI would be proportionately increased, and would bepreferably a multiple of seven segments.

In addition to the signal transmitting rings of the distributor D, it isconventional to provide segmented local ring R2 and an energy feederring R4 associated therewith whereby the cyclic operation of variousmechanisms at the transmitting station may be properly timed.

The brush I3 successively bridges the segments of ring RI across to ringR3 and brush I2 functions in a similar manner to bridge rings R2 and R4.The brushes I2 and I3 are insulated from one another but are mounted forsynchronous rotation, being preferably driven by a synchronous motor(not shown) which is held in step with other elements of the multiplextelegraph system in accordance with any of the usual methods ofsynchronization.

Where it is not desired to provide for the transmission of auxiliarysignals other than those originating from the transmitting tape II thecode signalling tongues I! of the keyer 8, are connected to thecorrespondingly designated segments of the signal distributor ring RIwithout passing through the auxiliary signalling device TS which iscommonly known as a tape stop unit.

, The need for transmitting auxiliary signals independently of anysignals which have been perforated in the tape II will be apparent tothose skilled in the art.

The special service signals to be transmitted by means of a supplementalsignalling device TS are those for instance whereby one or more taps ofa bell may be produced at the receiving end.

In consideration of this requirement it is customary to connect a tapestop auxiliary unit TS between certain of the code signalling tonguesI-'I of the keyer 8 and the signal distributor ring RI.

The automatic signalling device, enclosed within the dotted rectangleTS, normally comprises cam operated switches SI to S5 interposed in theleads connecting the code controlled tongues 2 to S of the unit 8 to thecorrespondingly designated segments of the ring RI of distributor D.

The spring controlled switch tongues TI to T5 of switches SI to S5 areadapted to ride over the peripheral surfaces of cams CI to C5respectively and have front and back contacts associated therewith. Thetongues TI to T5 of switches SI to S5 are connected respectively to thesegments 2 to 6 of ring RI on distributor D. The individual frontcontacts FCI to F05 of switches SI to S5 are connected respectively tothe code controlled tongues 2 to 6 of the unit 8 whilst the backcontacts BCI to B05 respectively of switches SI to S5 are connected topositive B supply source 9.

The peripheral surface of each cam 01 to C5 is provided with one or morehumps or the like which function to operate the associated springcontrolled tongues TI to T5 from the front contacts of switches SI to S5to the back contacts thereof, in different positions, of the cams. Theshape and disposition of said humps differ for each cam and said humpsare so disposed that simultaneous movement of the cams through apredetermined angle causes different positive potentials andconsequently different code charactors to be set up on the segments ofdistributor D.

The cams CI to C5 are fixedly mounted on a cam shaft 25 in such a mannerthat the physical relationship between the peripheral humps in theindividual cams, at predetermined angular settings of the shaft, willcause the setting up of code characters on the distributor segments inpredetermined sequence.

The tape stop unit TS is provided with a dialing member I4 for specialtransmission of a series of code signals. The extent of movement of thedialing member I4 is determined by placing a finger in any one of theholes I5 and movng the member in the direction indicated by the arrowuntil the finger strikes a stationary stop I5.

The operator then withdraws his finger from the selected hole I5 therebyreleasing the dialing member I4 for restoration to its normal positionunder the influence of a coiled spring II, this spring having beentensione'd by the previous manual dialing operation. A gear I8 isloosely mounted on the shaft I9 and has projecting therefrom a pivot pin2!! for supporting a pawl H which is adapted to engage with the teeth ofa ratchet wheel 22 fixedly mounted on shaft IS. The dialing member I4and a switch controlling dog 23 are also fixedly mounted on the shaftI9. During the dialing operation, the teeth of the ratchet wheel 22 slipunder the pawl 2| but during the return motion of the shaft I9 the pawl2| is engaged by a tooth of the ratchet wheel 22 and caused to rotatebackward with the shaft I9 and with the latter locked to gear I8therebyimparting rotation to the pinion 24 fixedly mounted on the shaft25. This shaft 25 also carries the series of code impulsing cams CI toC5 inclusive and a ratchet wheel 26 all fixedly mounted thereon,

In conventional tape stop units only 5 cams are employed; however incarrying out the present invention an additional cam C6 is provided.

The cam shaft 25 can rotate only as permitted by the operation of anescapement 21 whose arms 21a and 211) are integral with an armature 28which is under control of a pulsating magnet 29. The impulses foractuating the magnet 29 are derived from the source B fed throughdistributor ring R4 and across brush I2 to segments 8, 9, I0 of ring R2.This circuit may be further traced through conductors 30 and SI tocontact springs 32 and 33 and thence to the windings of magnet 29 andfinally returning to the negative side III of source B.

In the transmission of ordinary traffic signals, the perforated tape IIis fed at a cyclic rate through the transmitter T in accordance with astep-by-step feeding thereof as indicated by the use of ratchet wheel 65and associated driving mechanism under the control of the operatingmagnet 35. This magnet is energized by the closing of a circuit throughthe two coils of a differential relay 36 which, when both coils areenergized, provides no attraction upon the relay armature 39. However,the energizing impulse for magnet 35 is derived from positive potentialsthrough ring R4 and certain segments of ring R2 when they are bridged bythe brush I2.

The relay 35 is designed to operate when one only of its windings isenergized but will not operate when both windings are energized;

normally, the local puls s. which are derived from segments 8;, 9 andill in distributor ring R2 will be branched so that, both windings. ofrelay 36 will be simultaneously and equally energized. The branch forthe left hand winde ing of relay 36 may be traced from conductor 30through conductor 3| to contact 32 and a companion contact 34 and thenceover conductor 58 to the left hand winding of relay 36. The branch forthe right hand winding may be traced from conductor 30 through the(Jo-operating contacts 38, 40 of relay 36 to the right hand winding.From the center tap of the winding of relay 36 the currents from bothhalves of the relay flow through a common conductor 5| and the windingof relay 35 to the negative terminal til-of the B supply.

When auxiliary service signals are to be transmitted the operatingimpulses are transferred from the magnet, 35 of the transmitter T to themagnet 29 of the TS unit upon the operation of dial member I l.

When the dial member I4 is manipulated the dog ity is withdrawn frompressure against the resilient spring 32. The tension on this spring 32urges it, when released, out of contact with spring 34 and into contactwith spring 33 which is in circuit with the winding of magnet 29. Theoperating impulses from the distributor ring R2 are thereforetransferred from the operating magnet 35 of the transmitter T to theescape-- ment magnet 29 of the auxiliary signalling device TS Dependingupon the hole l5 which is fingered, from one to five strokes of the bellwill be produced at the receiver. However, the shift signal, the bellsignal, and the unshift signal are required for each stroke of the bell.Consequently, the code determining cams CI to C5 inclusive are normallyprovided for setting up these code signals and for transmitting thesame. When the dialing member I4 is operated for the transmission ofauxiliary or Service bell signals, operation of the tape stop unit TSoccurs in the following sequence:

Upon each revolution of the brush l2 an impulse will be transmitted tothe escapement magnet 29. Each impulse causes the escapement wheel 26 tomove one step. Each movement of the escapement wheel 26 causes adifferent set of code characters to be applied to the segments 2 to 'linclusive of the distributor ring RI, the nature of the charactersdepending upon which of the control springs associated with theindividual cams is operated by the code character on the periphery ofthe cam. The code characters on the peripheries of the cams CI to C5,the arrangement of said cams, and the associated circuit wiring, isnormally such that the successive code characters transmitted to thedistributor RI correspond with the signals Shift, Bell signal, Unshiftin that order for each bell signal to be transmitted.

The code elements 3-45 have been arbitrarily chosen as the upper caseshift of Figure shift signal. When the figure shift signal istransmitted the peripheral code characters (humps) of the cams CI to C5are such as to cause the operation of the associated tongues of switchesS2S3S4 whereby a positive pulse is applied to each of the segments 3-4-5of the distributor RI The bell signal (following the figure shiftsignal) usually corresponds with the signal for the letter J but ifpreferred it may be the same signal as chosen for the letter S or anyother lower case character on the keyboard and when the escapement wheel26 moves the cams CI to C5 into position for the transmission of thebellsignal the peripheral humps of said cams operate the appropriateassociated tongues TI to T4 to cause positive pulses to be applied tothe distributor segments of Bi which correspond with the code charactersof the particular letter arbitrarily chosen for the bell signal.

In the next position of the escapement wheel 26 cams 0!, C2 and C3 arein position to elevate their tongues Tl, T2, Ttl respectively thereby toimpress positive current on distributor segments 2, 3, and 4. This is asignal arbitrarily chosen to designate the unshift or letter shiftfunction.

The steps of operation of the cams as thus far described are those whichwould be performed if the operator wished to transmit a single strokebell signal. It will therefore be appreciated that for the transmissionof five bell signals the peripheral characters on the cams must be suchas, to enable the above signals to be repeated five times with a normalor no signal condition separating each set, of signals during eachrevolution of the cams.

When the number of strokes of the bell is to be greater than one, theextent of the motion of thedialing member [4 is determined by the holel5 which is fingered by the operator, and accordingly any selected areof revolution of the cams may be traversed for transmitting a propersequence of signals necessary to produce the desired number of taps ofthe bell. Usually from one to five strokes are sufficient for all of theusual service signals such as start, re-run, repunch, stop and regulate.

It is, to be understood that the procedure outlined above it purelyarbitrary and that if character designations of the different codesignals were to be altered, corresponding changes would be made in thecircuit diagram.

During the transmission of the auxiliary shift, bell, and unshiftsignals it will, of course, be appreciated that the operation of thetransmitter T is temporarily interrupted. This interruption is attainedby opening contacts 32 and 34 which are included in the circuit to theleft hand winding of the relay 36.

As the code characters for a bell signal correspond with those of anarbritrarily chosen letter in the lower case the necessity for precedingand following the bell signal with shift and unshift signalsrespectively in order to differentiate between the two functions of thesame code characters will be obvious.

Because of this requirement there is a distinct possibility, as alreadypointed out, that if upper case characters such. as figures are beingsent when transmission is interrupted for the purpose of sending bellsignals with the auxiliary device TS, the letter shift signal whichfollows the bell signal is likely to cause the receiver to wronglytranscribe the code characters when the message signal transmission isresumed.

The modification necessary in accordance with this invention to avoidthe difliculties previously outlined and the manner in which thesemodifications. affect the operation of the auxiliary signalling devicewill now be described.

The additional apparatus employed in carrying out the present inventioncomprises an additional cam C6, a relay 3! having two separate windings,31a, 31b and polarized relays 42, 43, M and 45.

The additional cam C6 is provided with the same peripheral characters ascam CI and is fixedly mounted on the cam shaft 25 in such a manner thatits peripheral characters coincide at all times with the peripheralcharacters of cam C I.

The relays 42, 43, 44 and 45 are respectively connected between the codecharacter tongues 2, 3, 4 and 5 of the unit 8 and earth I0. Each of therelays 42, 43, 44 and 45 is provided with a movable contact member 52,53, 54 and 55 respectively and which, in the operated position, isadapted to make contact with an associated fixed contact 62, 63, 64 and65 respectively. The fixed and movable contacts of the relays 43, 44 and45 are energized by the positive potentials simultaneously set up ontongues 3, 4 and 5 of the unit 8 by tape perforations corresponding tothe figure shift or upper case signal and a circuit is completed fromthe +3 supply source through the contacts of relays 43, 44 and 45 andthe winding 31a of relay 31 to earth I whereby relay 31 is caused tooperate.

Energization of the differential relay 31 causes the operation ofassociated contacts of switch section S8 which functions to complete aholding circuit from the +3 supply through the winding 31a of thedifferential relay 31 to the earth or negative terminal I0 of the Bsupply. The completion of this circuit ensures that the relay willremain energized irrespective of subsequent polarity variations of thetongues 3, 4 and 5 until de-energized in a manner hereinafter to bedefined. The operation of switch section S8 also serves to transferpositive battery from the contact BCI of switch SI to the contact BC6 ofswitch S6.

The operation of the differential relay 31 serves also to operate themoving contact arm of the associated switch section S1. When relay 31 isenergized, the closing of contacts at S1, provides a path for a spacingimpulse to pass to number 2 segment, of the transmitting distributor RI,every time the third step of each bell ringing cycle is transmitted. Asthe positive supply has been removed from switch SI, and applied toswitch S6, and as the contacts TI and T6 respectively controlled by camCI and cam C6 both lift at the same instant, then number 2 segment ofthe distributor RI would be left open if contact S1 were not provided.

The modifications required to carry out the present invention arecompleted by connecting the cam contact spring T4 of switch S4 to thenormally closed contact FC6 of switch S6 while the cam contact spring TBof switch S6 is connected to No. 5 segment of the distributor RI. Theimpulses of cam C4 now pass through switch S6 to segment 5 of thedistributor RI.

The operation of the modified tape stop unit or auxiliary signallingdevice: TS in accordance with the present invention is as follows:

In the normal signalling conditions involving the transmission ofletters of lower case characters the normal operation of the apparatusis not affected, the code characters set up on the tape controlledtongues I to 1 being applied to the correspondingly designated segmentsof the distributor RI. In the present example the tongues I and 1 aredirectly connected to their associated distributor segments whilsttongues 2, 3, 4, 5 and 6 are connected to the corresponding segments ofthe distributor RI through contact members associated with cams CI, C2,C3, C4, C5 respectively, when said cams are in their normal positions.When a figure shift signal is set up on the tape controlled tongues 3, 4and 5, by perforations in the tape and for the purpose of transmittingthe signal required to condition the receiver to receive upper casecharacters, positive potentials are applied simultaneously to thesegments 3, 4 and 5 of the distributor D and to the relays 43, 44 and45, causing said relays to operate their associated contacts 53, 54 and55 to close onto contacts 63, 64 and 65. The closure of these pairs ofcontacts results in the energization of the differential relay 31 andthe operation of switches S1 and S8. As already explained, switch S1functions to transfer negative battery to No. 2 segment of thedistributor RI when switch SI is in the open position, and switch S8transfers positive battery from switch SI to switch S6, also completinga holding circuit from +B supply through winding 31a to earth.

The normal transmission of the code characters, set up on the codecontrolled tongues I--1 by the perforated tape II to the correspondinglydesignated segments of the distributor RI is not affected by the circuitalterations brought about by the operations of the relays 43, 44, 45 andthe differential relay 31 so long as the auxiliary signalling device TSis not operated to cause the transmission of service bell signals.

If however the auxiliary signalling device TS is operated for thepurpose of transmitting bell signals during the transmission of signalsof upper case characters, such as figures, the transmission isinterrupted by the opening of the contacts 32, 34 which causes thetransmitter II to stop. Closure of the contacts 32, 33 completes theenergizing circuit of the escapement magnet 29 and when the dialingmember I4 has been moved to the position corresponding to the number ofbell signals it is desired to transmit, the cams CI to C6 will beactuated by the escapement wheel 26 for the purpose of transmitting thedesired signals in the manner and sequence already described, throughswitches SI to S6.

However, due to the operation of the differential relay 31, positivecurrent has been removed from switch SI and applied to switch S6;therefore signal characters requiring a positive pulse on segment 2 ofthe distributor RI, such as the unshift or letter shift signal whichcomprises positive pulses on segments 2, 3 and 4 cannot be transmitted.As the cam C6 is an exact duplicate of cam CI, when the peripheral codecharacters on cam CI are in position to lift the associated contactspring TI, the peripheral characters of cam C6 are similarly positionedto lift the associated contact spring T6 and cause positive current tobe applied to segment 5 of the distributor RI.

It will thus be seen that a positive potential is applied to segment 5Whenever a positive potential is required on segment 2. The unshift orletter shift signal 2, 3, 4 is therefore transmitted as 3, 4, 5 which isthe code character arbitrarily chosen as the case shift or figure shiftsignal.

From the foregoing it will be seen that so long as the differentialrelay 31 remains energized the letter shift signal 2, 3, 4 which followsthe bell signal will be changed to the fi ure shift signal 3, 4, 5 andthat when the bell signals are completed and transmission from theperforated tape I I is resumed the receiver will continue to transscribefigures or upper case characters.

This condition will continue whenever the auxiliary signalling device TSis operated until such time as a lettershift signal corresponding with 9the code character 2, 3, 4 is set up on the code controlled tongues '2,3, 4 of the keyer 8 by the perforated tape H. s

When positive potential appears on the tongues 2, 3 and 4 the relays 42,43 and 44 close their associated contacts. The operation of thesecontacts completes a circuit which can be traced from the +B supplythrough the contacts of relays 43, 44, 45 and 42, the second winding31b, of the diiferential relay, to the earth or negative terminal ll! ofthe B supply.

Completion of this circuit causes current to flow through the secondwinding 31b of the differential relay3'l. The direction'of current flowthrough the second winding 31b of the differential relay 3! is such asto create an opposite magnetic field to neutralize the field produced bythe current flowing through the first winding 31a, and allow the contactswitches S! and S8 to open or resume their normal unoperated condition.

The opening of switch S1 again allows the impulses to normally passthrough switch SI controlled by cam Ci. The return of the switch S8 tothe normal position removes the positive battery from switch S6, andrestores it to switch SI and removes the holding current through thewindings of the coil 31a.

If the differential relay 31 is not operated when letter characters onthe perforated tape l I, set up code controlled tongues 2, 3, 4 in theunit 8, then the positive potential from the transmitter tongues 2, 3',4 causes relays 42, 43 and 44 to operate their associated contacts. Now,although a circuit is formed from +B supply through coil 37b to earth,the relay 3! is not energized because the current is so regulated (byresistors 56, 61) that it is not sufficient to energize coil 31b, yet itis sufficient to release the energized coil 31a.

When the difi'erential relay 3! is not operated and letter charactersare being transmitted when the transmission is interrupted by theauxiliary signalling device TS, the normal functioning of the auxiliarysignalling device TS is not affected.

Bell signals preceded by the shift signal and fol-' lowed by the unshiftor letter shift signal Will be transmitted by the device TS inconventional manner. In this case since the letter shift signal followsthe final bell signal the receiver will continue to transcribe lettersor lower case characters when transmission from the perforated tape isresumed.

I claim:

1. A code signalling system comprising a tape controlled transmitterunit, a code element keyer,

a distributor, an auxiliary signalling device inter posed between saidkeyer and said distributor, said device constituting means fortransmitting a train of code signals which includes an uppercase shiftsignal, a bell signal and a lowercase shift signal in succession; aplurality of cams and associated switch contacts located in saidauxiliary signalling device for producing said train of code signals,one of said cams being effective in cooperation with a differentialrelay to reverse the sense of a certain case shift signal, meansincluding storage relays operable in response to the keying of anupper-case shift signal by said keyer for nullifying the eifect of alower-case shift signal subsequently keyed by said auxiliary signallingdevice, and means for deenergizing said relays in response to alowercase shift signal initiated by said tape controlled transmitter.

2. A code signalling system according to claim 1 wherein there areprovided an even number of polarized storage relays.

3. A code signalling system according to claim 1 wherein there areprovided a differential relay in the means for de-energizing the storagerelays.

4. A code signalling system comprising a tape controlled transmitterunit, a code element keyer, a distributor, an auxiliary signallingdevice transposed between said keyer and said distributor,

said device constituting means for transmitting a train of code signalswhich includes an upper-case shift signal, a bell signal and a lowercaseshift signal in succession; means including storage relays, each of saidstorage relays being provided with a moving contact which, whenoperated, is adapted to make contact with an associated fixed contact,three of said fixed contacts being energized by positive potentials setup on selected elements of said .code element keyer by means of tapeperforations corresponding-to figure shift or upper-case signals, meansincluding a differential relay having a locking circuit effective uponclosure to retain the efiects of operation of said storage relaysnotwithstanding subsequent polarity variations caused by said auxiliarysignalling device.

IAN N. McBAIN.

REFERENCES CITED The following references are of record in the

